An omnidirectional camera provides for an omnidirectional image to be photographed in a single shot by using a camera configured by combining a special optical system such as a fisheye lens, spherical mirror, or the like with an ordinary camera (see Non-Patent Literature 1, for example). Omnidirectional cameras are used in a wide range of fields, including monitoring systems. However, in an omnidirectional image there is major image distortion of people, objects, and suchlike individual photographic subjects (hereinafter referred to as “monitoring objects”), making it difficult to grasp the appearance of individual monitoring objects.
Thus, technologies have hitherto been proposed that perform image processing on an omnidirectional image (see Patent Literature 1 and Patent Literature 2, for example). The technology described in Patent Literature 1 converts an omnidirectional image to an annular image—specifically, to an image displayed within an area between two larger and smaller ellipses with different center positions. By means of this technology, it is possible to easily grasp the positional relationship of individual monitoring objects. The technology described in Patent Literature 2 performs coordinate conversion of an omnidirectional image to a panoramic landscape-format image, and performs distortion correction by clipping an image of a specified monitoring object. By means of this technology, it is possible to generate an image with little individual monitoring object image distortion from an omnidirectional image.